Utensil



1 2 March 22, 1927. D- E. SHAW 6 1 758 UTENSIL Filed May 17. 1922 I FIG/.1

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WITNESSES ATTORNEY 45 nanareaarrangemen c lhe inven on relatesgto electrical heating apparatus; and T i'norei particularly to 7 uten- Isi lsfor domiesti c or; industrial use."

" The object}of1tliis'invention? is to usea' 5 heating element comprising; a' conducting "wire of low resistivity .or very good conduct-i rit y, and preferably one I having, a positive temperature coefficient of resistance, such as a single substantially pure metahtheele- 1o ment (being Lat-ranged: in closely related lengths ahoutia receptacle and being small i n .crossi-section' fsofthata great number of "lengths or;turns:;may 'be-, ma 'de,on the utensil orreceptaclestoibe heated for, aflgiven current consumptioniinxcorderto :secure a greater cont-actingisui'face." ;.In1,order;also

. to further'i crease theqtransfer. ofheat by conduction:thelelement is brought into ivery .close. relationflwith the :walls ofrthe rece'p- .ta cle to 'beheated and. insulated therefrom by a,; .very Ith inclayers or {coating 7 of binding material, iflandgt he jwir'eipreferably" used is one having :a: thiirrenamel insulation coating. l The gturnsiofjthis'wire are practically 2 in contact, with each; other and: the exposed portionsgof theeleme'nt' are shutoff from the air 'or,other-;gaseous; medium by a coating of flinsulating; material. -With this, consanction"Iihaveiound th t hecur t 0 Sllllled in doing a given amount of cooking 'in the. container embodying the invention is much-less than'is usual in-electricalcooking .utensils. -11 7 3:, 5.

' :1 1aAafm herio iec -ott ein e tio ism provide an electrical heating apparatus having .jouter-iand" inner receptacles, the;z heating-"elen ent be ng 'i I 9U 1 Q b t e ne r c pt c andthe space between; the receptacles, withinwhiclrthe element isenclosed having the 40 L j e h s edthe eimm I r '..-A f rt r Object: of thein nti n i to rr v d n. e r c he app at s. n wh iv able he t ma h mp e o t I f rthe r eze hi eerie to pro-ride heating. 7 element ain :which both the working, and; an te. temperature V can -L a ns.-

hi hvpesit re te p ratur o t t e e n thefl eesequ e is i or irtInwAUKEE, WISCONSIN.

the top of the outer container and depending ontaine y varying, the circuit arrange- Apfili'catioiifiled'Iay' 17, 1922.. Serial No. 561,673.

crease in the consumption of current as the temperature developed therein increases. By the proper choice of these factors, I construct each utensil so that it will do the character of cooking it is designed for quickly, and can control it so that itwill not develop a temperature sufiiciently high to burn the substance being heated or destroy the heating element or the container to which it is attached if empty. v

A further object of the invention is to arrange the connections between the container and the source of current supply so as to eliminate any danger of shock when the utensil is touched by a person in contact with the ground. With the above and other objects in view the invention consists in the construction and the several features of construction hereinafter described and all equivalents.

' In the drawings: Fig. 1 is a vertical sectional view through a heating appliance embodying the invention; Fig. 2 is a diagrammatic view of the wiring system for the element. p

In the drawings I have illustrated a utensilembodying the invention, comprising an inner receptacle or container 3 and an outer container 4, the inner container resting upon into the same to provide a space 5 between the containers. I desire it to be understood, however. that the invention is not to be limited to the particular form or shape of .the

container herein illustrated, as the utensil may be a coftee-pot,'a trying-pan, oven, or

other device in which the material subjected to heating or cooking is placed in the inner' container.

The inner container 3 is preferably of socalled enamel ware, that is, the metal body -6 has an inside coating 7 and an outside coating 8 of enamel or other suitable hardenedinsulating material. I The heating element 9 is preferably a very 1 0 fine wire of highconductivity wound around the outside of the container 3. By fine wire.

I mean a wire on the order of 27 B. 8: S. auge orless. This wire preferably is substantially mono-metallic so that it has a positive, and preferably high, temperature co-efiicient of resistance, and the convolu- -tions while touching each other are practically insulated from each other by a very film of 'nsulating material with which 19 fore there is very wire, preferably a single layer, is wounddirectly on the inner container. Moreover, the enamel is a fair heat conductor and dampness will have no bad effect on windtlvely much ings thus insulated. However, as the enamel coating 8 presents a slippery surface, I coat this enamel surface prior to winding with a thin semi-liquid coating of insulating material, such as sodium silicate thickened with whiting, which fills in the exposed spaces between the convolutions of the wire and between the wire and the container, and which hardens as soon as it-is subjected to the heat developed by a clirrent of proper strength passin through the wire, whereby the element is firmly bound in close contact with the receptacle and is cut off from the air or other gaseous medium. By adopting this construction the insulation betweenthe;

metal and the element and between the com volutions of the element is far thinner than could be obtained by solid insulation, the

heat developed in the element is transmitteddirect to the metal of the container and thence to the material within it substantially by conduction through this binding materlal with a very low temperature difference.

Theutensil is primarily designed for 'cook- 'ing or baking so the ultimate temperature;

required is never greater than 500 Fahrenheit and it is therefore possible to use insulating material of much lower heat resisting properties than would be the caseif the wires were allowed to reach a higher temperature.

Furthermore, as the radiatmg surface of the inner container is relagreater than that of the currentcarrying heaflproducing unit 9 it radiates the heat conducted from the element very readily and is preferably so designed that the maximum temperature developed when the utensil is empty will not be sufficiently highto cause injury to the heating unit or the utensil. Also by using an element having a positive; temperature coeflicient of resistance the resistance of the wire increases as the temperature rises so that the current consumption decreases asthe temperature of the receptacle and'its contents rises.

Anotherifact to be noted in connection with this construction is that the quantity of heatdeveloped by the element is greatest the container. 'circuit with the plugs -12 and 14 and the directl '23.

conductor 19 connects the when the container and its contents 'are coldest and gradually diminishes as the temperature of the whole mass rises, and since the element is so closely associated with the v '70 receptacle that there is' little difference between the temperature of the element and the contents of the receptacle the desired is 7 preferably this purpose I arrange three sets of plugs on the receptacles, one set comprises 'plugs' 11 and 12 for the low heat, another comprising plugs 13 and-14. for the medium heat and another set comprising plugs15 and 16 for thehigh heat, the plug having one-half 16" insulated from the container and the other half 16' grounded on One end of section Bis in part 16f of the plug 16, the element 20' 16 being a split plug representing such plugs in Fig. 1', and being .secured to the container b 'nuts conductor 18 connects the 13 and 15 with the sections A and anda plug 11 and the other part 16" of the lug 16 with one end of the section A. 1th this construction when'the supply circuit is connected to the plugs 11 and v12 current passes from the plug 11 thr'ou h the conductor 19, sections A and B to p plug 12. When the supply current is connected to .the plugs 13 and 14 current pames from the plug 13 to conductor 18, section B, the containers 3 and 4 to ,plug 14. 'When the supply circuit is connected to the plug 15 and 16 current passes from the plug 15 through conductor 18' from which part of the current flows through section B to containers 3 and 4 and thenceto part 16', and part of the current flows through section A to part 16" of the plug 16, aswill-be appar cut when the connections for the plugs are described.

ug 12, containers 3 and'4- to The insulating plugs 11, 13, 15 and16 H each comprise a member 20, preferably made hollow so that the wires connected with these plugs may be drawn throu h the openings in such plugs. These mem ers are secured by nuts 23 or other suitable means. A pas-f sage in one of the hollow plugs above 'de scribed may be used for the purpose of exhausting air from the space 5,the outer ends of each of these hollow plugs being sealed providing a vacuum space between the containers heat conduction losses fromthe inner to the outer container are minimized and to to the outer container in any suitable mana plug 25 or otherrsuitable means. By p efiectually seal the containers together the upper beaded edge 26 of the container 4 is pressed into and interlocked with an annular groove 27 formed on the inner container; In

the split. plugit will be understood that the parts 16' and 16" are suitably separated from each other by insulating material.

In each instance connection with the supply circuit 28 and 29 is made by a fixed contact 30 and a flexible contact 31, respectively,

- connected to the wires 28 and 29. Either set along the support 32 to bring the desired plugs into engagement with the contacts 30 and 31. As contact 31 is resilient it will act combination with a heat-conducting conto press the upper plug into engagement with the fixed contact as well as make a good contact with the lower plug. The grounded side of the line is always connectedto contact 31 so that therewill be no voltage difierence between the container and the ground under any conditionsw I desire it to be understood that this invention is not to be limited to any specific form or arrangement of parts except in .so far as such limitationsare specified in the claims;

What I claim as my invention is: a

1. In an electrically-heated utensil, the combination with a heat-conducting container, of a heating element com rising a copper wire coated with a very thin eat-cons ducting, moisture-proof insulating film, said wire being closely Wound with contiguous convolutions about said container, and means for supplying current to said element.

2. In an electrically-heated utensil, the

tainer, of a' heating element comprising a fine enamelled wire of substantially pure copper wound with contiguous convolutions in close thermal relation to said container,

hausted from the space between saidcontainers, a heating element attached to the inner container, and means for supplying current to said element.

combinationwith'a container, of a heating element attached thereto, plugs secured to the terminals of said element, one of said plugsbeing grounded tot-said utensil, means for supplying current to 'said element on connection with said plugs, and means whereby the grounded plug is connected to the 2' 5. In an electrically-heated utensil, the

grounded supply line before the other plug can be connected to the other line.

6. In an electrically-heated utensil, the combination of an inner container, an outer container. spaced from the inner container, aheating element within the space between said containers and attached to the inner container, and means for exhausting airfrom the space between the containers including a contact plug secured to the outer container and having an exhausting pas-- sage therein.

-7. In an electrically heated utensil, the

combination with a container, of an en amelled copper wire closely wound around said container in close thermal relation therewith, said wire having a gauge thickness of 27 B. & S. gauge or less and a neglible potential difference between turns. Intestimony whereof, I afiix my signature.v

- DAVID E. SHAW. 4 

